The myth of Rockwool
- Thread starter tannaberton
- Start date
JohnDee
Well-Known Member
You never squeeze rochwool. That collapses the structure making it worthless.
I bought 4 cases really cheap at an auction so I'm sorta stuck with it.
I like doing seedlings and clones with it. Soaked to 5.5 ph.
And the bulk of Holland is fed by the stuff via huge commercial greenhouses...but they don't squeeze it first.
JD
I've used rockwool from day 1. Many years back.
Germinate seeds in paper - so I can see they are viable.
Transfer to small rockwool cube. lightly water so it is "half" soaked.
Don't water again until it is nearly the weight of a dry cube. Nearly!
Once the seedling is showing I just dab the cube bottom in a saucer of water/nutes. Watch it soak up, pull away when it is a bit heavier.
When tap root shows, transfer to big growdan / RW big cube.
Water medium, so it is all wet, but around half the weight of fully soaked.
Don't water until it gets much lighter.
Water by dabbing, same as big cubes.
When roots show, I put them in a NFT tray , no matting, pump on twice a day for 1 minute.
When lots of roots show, put in main NFT tank on matting.
That's it.
The trick with rockwool is to learn the weight of dry and saturated. You learn very quickly. Just don't saturate them until they are in the big cubes.
Germinate seeds in paper - so I can see they are viable.
Transfer to small rockwool cube. lightly water so it is "half" soaked.
Don't water again until it is nearly the weight of a dry cube. Nearly!
Once the seedling is showing I just dab the cube bottom in a saucer of water/nutes. Watch it soak up, pull away when it is a bit heavier.
When tap root shows, transfer to big growdan / RW big cube.
Water medium, so it is all wet, but around half the weight of fully soaked.
Don't water until it gets much lighter.
Water by dabbing, same as big cubes.
When roots show, I put them in a NFT tray , no matting, pump on twice a day for 1 minute.
When lots of roots show, put in main NFT tank on matting.
That's it.
The trick with rockwool is to learn the weight of dry and saturated. You learn very quickly. Just don't saturate them until they are in the big cubes.
NFT seems like a cool solution to use. Do you find any issues with salt buildups by not top feeding at all? Do you flush or leach throughout your grow?
Also, what do you mean by "watering by dabbing"?
Hope you don't mind the questions, thanks!
ThaMagnificent
Well-Known Member
Rockwool chunks only in my ebb and grow setup. Rockwool sucks for seed starting though
Seems as though we all get them too wet. I always thought it was supposed to be impossible to over irrigate but ive since learnt otherwise..
coreywebster
Well-Known Member
If I could like that comment 100 times I would!
I hate the stuff
ThaMagnificent
Well-Known Member
You want it too wet otherwise plants fall over on a table
I have in the past let my rockwool dry out almost completely before irrigation and I have 1 metre tall plants that don't fall over. Id rather use supports if they did fall over, than overwater rockwool.
I forget the %. But there is an optimum moisture content for rockwool, and im figuring out now optimum times for re irrigation.
mytwhyt
Well-Known Member
Anyone get around to reading this thread? Only reading the first post would help.. Personally i think RW sucks..
https://www.rollitup.org/t/a-batch-of-clones-in-rockwool.15030/
https://www.rollitup.org/t/a-batch-of-clones-in-rockwool.15030/
JohnDee
Well-Known Member
Ya Al B. Fuct knew rockwool...that's for sure.
The OP was squeezing his rockwool, thus ruining it...and then blamed the medium. Go figure...
JD
ThaMagnificent
Well-Known Member
I have to put small rocks in the bottom of my solos when they get too talk and it dries out too much
Mellow old School
Well-Known Member
There are ups and downs with rockwool, but if you monitor your seedlings closely in it the first 3 weeks, you can do well, but they do tend to dry out quickly sometimes, when temps are high...works great for clones...
Sorry for the late reply, not been on for a while.
Water dabbing - holding the RW cube, and dabbing it in shallow water/nutes. So it soaks up form the bottom, like a sponge. Doing it this whay you can feel the weight change each time you "dab". You very quickly get a feel of what is wet enough.
NFT -
no salts build up.
no top feeding - all the roots come out the bottom of the cube. I'll put a pic up later of my current roots of both grow rooms.
Flushing - I fill the tank up (45 litres), add nutes, PH balance (1ml of PH up for me), and then let the plants drink it all up until it comes close to low enough for the pump to be exposed. Then I fill up with fresh water, add nutes, PH up, and repeat. This way it's almost getting a complete flush each time (more like 30-35 litre flush with 10-15 litre old water in there).
During veg one tank lasts ages at first. I'll completely flush the tank after a couple weeks as it uses very little water and I want it refreshed. I use the NFT pump to do the draining.
Once veg is well underway the tank needs topping up around once a week.
When I switch to flower I drain again after preflowering is done. I'll now use bloom instead of grow nutes.
During flowering it's a once a week tank top up - maybe more often in the last few weeks.
Once or twice during flowering I'll do a complete tank drain instead of a top up, just to keep things in order (you do see some salt residue in the tank itself, from the nutes, which affects nothing)
Last 3 days I run just water to flush the nutes out.
So overall, I drain and refil the tank around 5 times throughout the whole cycle. The rest of the time it's a case of topping up from nearly empty , to full.
Notes:
- when summer is here, they drink the water so fast I use an auto top up system - a large 110 litre tank with fresh water that tops up the rez with an aquarium top up system. This works great. Hardly ever have to intervene - just add nutes here and there. This doesn't work so well in the winter as they don't drink so fast and I want the solution refreshed more often as the plants drink the nutes faster than the water so you end up with an imbalanced nutes mix after a while.
I also have an NFT tank that has a 100 litre rez and I don't like it. Reason being that it holds too much water! - all of the above becomes much harder when the rez doesn't get low for two to three weeks. I end up flushing good nutes away as I want a tank refresh occasionally but it just hasn't gone down much! Fill it up less you say! - problem is the much bigger pump needs a lot of water to cover it.
Mate of mine just switched from soil to NFT and he's amazed at the speed of the growth.
I would add that I started on RW, and I'm sure there are better alternatives out there, but I know it, so I stick with it.
RW is very easy to over soak, it's also very easy to dry fast without noticing. Bone dry. This is all only an issue during seedling/cutting stages. Once in an NFT tank its all irrelivant.
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Thanks for all the advice that must've taken you a while to write up, appreciate it!
I'm also in the same situation, only ever grown in rockwool and watering by hand is a drag. NFT seems like a easy way to deal with that issue! It's either that or a undercurrent hydro system for me.
Do the yields go crazy like rDWC too? Excited to see your root growth. If you've got any grow journals on here ill check em out, curious to see what fruits you pull in that system. Sounds awesome.
No probs. I'm a fast typer, and I like to share what I've learnt 
NFT is easy and cheap. The ONLY thing with NFT is to wait until you have sufficient roots coming out of your rockwool before switching the pump on 24/7. Until there are a handful of healthy root "teeth" coming out of the bottom of the cube, just switch the pump on for a couple of minutes, twice a day. Once you see roots coming out and away from the cube, whack the pump on 24/7. They then go nuts! I'm not experienced in DWC, but it's the same theory. Give the roots the perfect environment. Water, air, food.
The animated GIF is 11 days, under NFT, Veg, 400W MH (including leaf trimming, which you can see) , switching to two small LEDs for one day when my light ballast died.
Below are the roots from my GT424 (45 litre) NFT tank, 4 weeks into flower (including preflower).
Below are the roots and cubes in my GT100 (100 litre) NFT tank. 2 weeks into preflower (2 weeks behind the smaller tank, but allowed to veg larger).
Notice how healthy the roots are (they are white in normal light), and how the cubes are fallen over - that's just the way the scrog netting and my LS-Training has forced the plants at angles. No harm done whatsoever. Shredded wheat
Below are some shots of a grow getting close to cropping. I'm getting about 12-15 oz dry from a 4x4 tent ( I don't keep records).
NFT is easy and cheap. The ONLY thing with NFT is to wait until you have sufficient roots coming out of your rockwool before switching the pump on 24/7. Until there are a handful of healthy root "teeth" coming out of the bottom of the cube, just switch the pump on for a couple of minutes, twice a day. Once you see roots coming out and away from the cube, whack the pump on 24/7. They then go nuts! I'm not experienced in DWC, but it's the same theory. Give the roots the perfect environment. Water, air, food.
The animated GIF is 11 days, under NFT, Veg, 400W MH (including leaf trimming, which you can see) , switching to two small LEDs for one day when my light ballast died.
Below are the roots from my GT424 (45 litre) NFT tank, 4 weeks into flower (including preflower).
Below are the roots and cubes in my GT100 (100 litre) NFT tank. 2 weeks into preflower (2 weeks behind the smaller tank, but allowed to veg larger).
Notice how healthy the roots are (they are white in normal light), and how the cubes are fallen over - that's just the way the scrog netting and my LS-Training has forced the plants at angles. No harm done whatsoever. Shredded wheat
Below are some shots of a grow getting close to cropping. I'm getting about 12-15 oz dry from a 4x4 tent ( I don't keep records).
I usually like to let my rockwool a get rootbound before I upgrade to 6" but I'm definitely sold on NFT, been thinking about it for a while but you convinced me.No probs. I'm a fast typer, and I like to share what I've learnt
NFT is easy and cheap. The ONLY thing with NFT is to wait until you have sufficient roots coming out of your rockwool before switching the pump on 24/7. Until there are a handful of healthy root "teeth" coming out of the bottom of the cube, just switch the pump on for a couple of minutes, twice a day. Once you see roots coming out and away from the cube, whack the pump on 24/7. They then go nuts! I'm not experienced in DWC, but it's the same theory. Give the roots the perfect environment. Water, air, food.
The animated GIF is 11 days, under NFT, Veg, 400W MH (including leaf trimming, which you can see) , switching to two small LEDs for one day when my light ballast died.View attachment 4312145
Below are the roots from my GT424 (45 litre) NFT tank, 4 weeks into flower (including preflower).
View attachment 4312147
View attachment 4312151
Below are the roots and cubes in my GT100 (100 litre) NFT tank. 2 weeks into preflower (2 weeks behind the smaller tank, but allowed to veg larger).
View attachment 4312152
Notice how healthy the roots are (they are white in normal light), and how the cubes are fallen over - that's just the way the scrog netting and my LS-Training has forced the plants at angles. No harm done whatsoever. Shredded wheat
Below are some shots of a grow getting close to cropping. I'm getting about 12-15 oz dry from a 4x4 tent ( I don't keep records).View attachment 4312153
View attachment 4312157
How long veg times do you run now on this system? Or do you flip to flower right away?
I could probably fit 2 gt424's in my new room, 70quid a pop each is cheaper than buying tons of RW that's for sure. Also, how many plants you getting per system there in the 4x4?
Thanks man appreciate the knowledge
Usually I veg for 2 to 4 weeks , depending on how well they fill the space / I LST them. That is from small bushy plants from my nursery that have plenty of healthy teeth roots showing through the bottom of the growdan. I transfer from the littel cubes to the big cubes (growdans) as soon as I see one root!
I tried flipping to flower straight away but didnt like the smaller buds. Pain in the arse to harvest. (that's the animated GIF crop - hence 12 plants instead of my usualy 4 or 5 in a GT424).
4-5 plants in a GT424 (one in the middle with 5). Fills a 4x4 tent easily with a little LST training.
You'll laugh how fast they grown when you try NFT.
When you start, be sure to have a PH meter, and an EC meter.
Keep your PH between 5.5 and 6 ish. Add only 1ml of PH-up at a time, leave for an hour, then retest. You'll soon learn how much you need for yoru water (if any).
Keep your nutes at 50% max until you are well into veg. (1 or 1000 on your EC meter). I rarely run over 1500, veg or bloom. The nute manufacturers way over estimate what you need.
I use IONIC nutes, but I'm sure they are all much of a muchness.
Keep your roots in the dark - the lid the tanks come with (corex) are good for this. Plus white plastic sheeting.
A cheap aquarium heater keeps your nutes at 18-20.
Keep your PH-up bottle well away from the tank.
Go scrog or similar. You need something to support the plants. The WILL fall over at some stage otherwise
Enjoy
I tried flipping to flower straight away but didnt like the smaller buds. Pain in the arse to harvest. (that's the animated GIF crop - hence 12 plants instead of my usualy 4 or 5 in a GT424).
4-5 plants in a GT424 (one in the middle with 5). Fills a 4x4 tent easily with a little LST training.
You'll laugh how fast they grown when you try NFT.
When you start, be sure to have a PH meter, and an EC meter.
Keep your PH between 5.5 and 6 ish. Add only 1ml of PH-up at a time, leave for an hour, then retest. You'll soon learn how much you need for yoru water (if any).
Keep your nutes at 50% max until you are well into veg. (1 or 1000 on your EC meter). I rarely run over 1500, veg or bloom. The nute manufacturers way over estimate what you need.
I use IONIC nutes, but I'm sure they are all much of a muchness.
Keep your roots in the dark - the lid the tanks come with (corex) are good for this. Plus white plastic sheeting.
A cheap aquarium heater keeps your nutes at 18-20.
Keep your PH-up bottle well away from the tank.
Go scrog or similar. You need something to support the plants. The WILL fall over at some stage otherwise
Enjoy
DangerDavez
Well-Known Member
I use the little cubes to clone and start seeds. Never had issues. The trick is to let them sit in the seed starting tray with a heat mat or in the sun to get rid of some of the moisture. I have a little thing they sit in at the bottom of the tray and I then poor water into the tray just below where the cubes are sitting. This ensure they stay moist and not wet. Pretty much 100 percent success with seeds unless they are super old and a solid 90 percent I would say cloning which is better than my clone machines and easier to transfer.